Nine foreign tourists have been injured in an attack in Pakistan's North-West Frontier Province.

Police said the tourists - mostly Germans - had stopped near an archaeological site in the district of Mansehra, 150 km north of Peshawar - when there was an explosion.

Three Pakistanis were also injured in the attack.

The tourists were part of a tour that had left the city of Rawalpindi to retrace the route of the old Silk Road to China.

The victims were taken to a local hospital, but the secretary to the Interior Ministry, Tanzeem Noorani, said there were no serious injuries, and first aid treatment was sufficient.

The tourists have all been sent back to the capital with a police guard.

'Locally-made' bomb

Officials said the device used in the attack was crude and probably locally-made, but there was no indication of who might have been behind the attack.

A senior police official said he suspected what he called "local mischief makers" because the device was so unsophisticated.

Tourists on the area usually have a police escort, but this particular group were reported to have left without one.

There have been several attacks targeting foreigners in Pakistan recently - including the 14 June blast outside the US Karachi consulate, which killed 12 Pakistanis, and the 8 May car bombing near the city's Sheraton Hotel, which killed 14 people, including 11 French engineers.

Last week, Pakistani police published photographs of 10 alleged militants suspected of carrying out the deadly bombings.

In a major policy speech in January, President Musharraf said he would clamp down on militant groups, whom he accused of destabilising Pakistan and damaging the country's image.